198 



THE MARATTIALES 



Transverse sections of a very young sporophyte of Angiopteris show the same 



relation of the parts as in the other genera. The junction of the traces of the Hist. 

 second, and third leaves takes place at a very short distance below the stem apex, 

 which, as Farmer pointed out, shows an unmistakable apical cell ot sonuw hat irregu- 

 lar form. Compared with the other genera, the primary leaf trace in Angiopteris has 

 the xylem better developed, and composed of about half a do/en traeheids, where 

 the trace enters the stem. This primary leaf trace is concentric, as it is in the later 

 leaves, and not collateral, as it is in Danica (fig. 179). 



Near the point of the junction of the three primary traces, there may be seen 

 in the young traces from the second and third leaves the first tracheary tissue, 

 consisting of one or two tracheids. As the sections are examined lower down the 

 tracheary tissue of the second and third leaf traces increases in amount until it 

 forms a solid band, separated from the corresponding xylem of the primary leaf 

 trace by a band of parenchyma. The three leaf traces are now completely fused, but 

 the sections of the two xylems are perfectly evident, and this band of tissue between 



Fig. 180. 



A-D. Four sections of an older sporophyte than that shown in ftp,. 179. X40. 

 E. Stem apex. ■ 150. 

 I - Central bundle from transitional region. 

 G. Buniile of primary root. 



the two xylems (which really belongs to the ground tissue of the stem and not to the 

 stele itself) corresponds to the "pith" figured by Farmer and Hill for the transi- 

 tional region between the root and stem (fig. 180, C). Sometimes, in still lowei 

 sections, the two xylems are connected, but I have found no cases where the pith 

 was entirely surrounded by the xylem, and the two xylems of this axial strand merge 

 gradually into the two xylems of the diarch primary root (fig 179, G). I he endo- 

 dermis is clearly evident in the intermediate region and is recognizable also at higher 

 levels, but is less easy to distinguish. 



In a series of sections, from a plant in which the fifth leaf was just recognizable, 

 a section at the level of the stem apex shows the apical meristem to he composed 

 nt several large cells, one of which is probably the single apical cell, but this is not 

 easy to determine. The base of the fifth leaf is close to the apical group and the 

 section of its stele is indicated by a group of small cells close to the stem apex. I he 

 stele of the third leaf is clearly seen, separated from the fourth leaf by about one- 

 third the circumference of the stem. Below the stem apex these two leaf traits 



